Electronic Device Module Comprising an Ethylene Multi-Block Copolymer

ABSTRACT

An electronic device module comprises:
         A. At least one electronic device, e.g., a solar cell, and   B. A polymeric material in intimate contact with at least one surface of the electronic device, the polymeric material comprising an ethylene multi-block copolymer.
 
Typically, the polyolefin material is an ethylene multi-block copolymer with a density of less than about 0.90 grams per cubic centimeter (g/cc). The polymeric material can fully encapsulate the electronic device, or it can be laminated to one face surface of the device. Optionally, the polymeric material can further comprise a scorch inhibitor, and the copolymer can remain uncrosslinked or it can be crosslinked.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/826,319 filed Sep. 20, 2006 and U.S. Provisional Application No.60/865,953 filed Nov. 15, 2006.

FIELD OF THE INVENTION

This invention relates to electronic device modules. In one aspect, theinvention relates to electronic device modules comprising an electronicdevice, e.g., a solar or photovoltaic (PV) cell, and a protectivepolymeric material while in another aspect, the invention relates toelectronic device modules in which the protective polymeric material isan ethylene multi-block copolymer. In yet another aspect, the inventionrelates to a method of making an electronic device module.

BACKGROUND OF THE INVENTION

Polymeric materials are commonly used in the manufacture of modulescomprising one or more electronic devices including, but not limited to,solar cells (also known as photovoltaic cells), liquid crystal panels,electro-luminescent devices and plasma display units. The modules oftencomprise an electronic device in combination with one or moresubstrates, e.g., one or more glass cover sheets, often positionedbetween two substrates in which one or both of the substrates compriseglass, metal, plastic, rubber or another material. The polymericmaterials are typically used as the encapsulant or sealant for themodule or depending upon the design of the module, as a skin layercomponent of the module, e.g., a backskin in a solar cell module.Typical polymeric materials for these purposes include silicone resins,epoxy resins, polyvinyl butyral resins, cellulose acetate,ethylene-vinyl acetate copolymer (EVA) and ionomers.

United States Patent Application Publication 2001/0045229 A1 identifiesa number of properties desirable in any polymeric material that isintended for use in the construction of an electronic device module.These properties include (i) protecting the device from exposure to theoutside environment, e.g., moisture and air, particularly over longperiods of time (ii) protecting against mechanical shock, (iii) strongadhesion to the electronic device and substrates, (iv) easy processing,including sealing, (v) good transparency, particularly in applicationsin which light or other electromagnetic radiation is important, e.g.,solar cell modules, (vi) short cure times with protection of theelectronic device from mechanical stress resulting from polymershrinkage during cure, (vii) high electrical resistance with little, ifany, electrical conductance, and (viii) low cost. No one polymericmaterial delivers maximum performance on all of these properties in anyparticular application, and usually trade-offs are made to maximize theperformance of properties most important to a particular application,e.g., transparency and protection against the environment, at theexpense of properties secondary in importance to the application, e.g.,cure time and cost. Combinations of polymeric materials are alsoemployed, either as a blend or as separate components of the module.

EVA copolymers with a high content (28 to 35 wt %) of units derived fromthe vinyl acetate monomer are commonly used to make encapsulant film foruse in photovoltaic (PV) modules. See, for example, WO 95/22844,99/04971, 99/05206 and 2004/055908. EVA resins are typically stabilizedwith ultra-violet (UV) light additives, and they are typicallycrosslinked during the solar cell lamination process using peroxides toimprove heat and creep resistance to a temperature between about 80 and90 C. However, EVA resins are less than ideal PV cell encapsulating filmmaterial for several reasons. For example, EVA film progressivelydarkens in intense sunlight due to the EVA resin chemically degradingunder the influence of UV light. This discoloration can result in agreater than 30% loss in power output of the solar module after aslittle as four years of exposure to the environment. EVA resins alsoabsorb moisture and are subject to decomposition.

Moreover and as noted above, EVA resins are typically stabilized with UVadditives and crosslinked during the solar cell lamination and/orencapsulation process using peroxides to improve heat resistance andcreep at high temperature, e.g., 80 to 90° C. However, because of theC═O bonds in the EVA molecular structure that absorbs UV radiation andthe presence of residual peroxide crosslinking agent in the system aftercuring, an additive package is used to stabilize the EVA againstUV-induced degradation. The residual peroxide is believed to be theprimary oxidizing reagent responsible for the generation of chromophores(e.g., U.S. Pat. No. 6,093,757). Additives such as antioxidants,UV-stabilizers, UV-absorbers and others are can stabilize the EVA, butat the same time the additive package can also block UV-wavelengthsbelow 360 nanometers (nm).

Photovoltaic module efficiency depends on photovoltaic cell efficiencyand the sun light wavelength passing through the encapsulant. One of themost fundamental limitations on the efficiency of a solar cell is theband gap of its semi-conducting material, i.e., the energy required toboost an electron from the bound valence band into the mobile conductionband. Photons with less energy than the band gap pass through the modulewithout being absorbed. Photons with energy higher than the band gap areabsorbed, but their excess energy is wasted (dissipated as heat). Inorder to increase the photovoltaic cell efficiency, “tandem” cells ormulti-junction cells are used to broaden the wavelength range for energyconversion. In addition, in many of the thin film technologies such asamorphous silicon, cadmium telluride, or copper indium gallium selenide,the band gap of the semi-conductive materials is different than that ofmono-crystalline silicon. These photovoltaic cells will convert lightinto electricity for wavelength below 360 nm. For these photovoltaiccells, an encapsulant that can absorb wavelengths below 360 nm is neededto maintain the PV module efficiency.

U.S. Pat. Nos. 6,320,116 and 6,586,271 teach another important propertyof these polymeric materials, particularly those materials used in theconstruction of solar cell modules. This property is thermal creepresistance, i.e., resistance to the permanent deformation of a polymerover a period of time as a result of temperature. Thermal creepresistance, generally, is directly proportional to the meltingtemperature of a polymer. Solar cell modules designed for use inarchitectural application often need to show excellent resistance tothermal creep at temperatures of 90 C or higher. For materials with lowmelting temperatures, e.g., EVA, crosslinking the polymeric material isoften necessary to give it higher thermal creep resistance.

Crosslinking, particularly chemical crosslinking, while addressing oneproblem, e.g., thermal creep, can create other problems. For example,EVA, a common polymeric material used in the construction of solar cellmodules and which has a rather low melting point, is often crosslinkedusing an organic peroxide initiator. While this addresses the thermalcreep problem, it creates a corrosion problem, i.e., total crosslinkingis seldom, if ever, fully achieved and this leaves residual peroxide inthe EVA. This remaining peroxide can promote oxidation and degradationof the EVA polymer and/or electronic device, e.g., through the releaseof acetic acid over the life of the electronic device module. Moreover,the addition of organic peroxide to EVA requires careful temperaturecontrol to avoid premature crosslinking.

Another potential problem with peroxide-initiated crosslinking is thebuildup of crosslinked material on the metal surfaces of the processequipment. During extrusion runs, high residence time is experienced atall metal flow surfaces. Over longer periods of extrusion time,crosslinked material can form at the metal surfaces and require cleaningof the equipment. The current practice to minimize gel formation, i.e.,this crosslinking of polymer on the metal surfaces of the processingequipment, is to use low processing temperatures which, in turn, reducesthe production rate of the extruded product.

One other property that can be important in the selection of a polymericmaterial for use in the manufacture of an electronic device module isthermoplasticity, i.e., the ability to be softened, molded and formed.For example, if the polymeric material is to be used as a backskin layerin a frameless module, then it should exhibit thermoplasticity duringlamination as described in U.S. Pat. No. 5,741,370. Thisthermoplasticity, however, must not be obtained at the expense ofeffective thermal creep resistance.

SUMMARY OF THE INVENTION

In one embodiment, the invention is an electronic device modulecomprising:

-   -   A. At least one electronic device, and    -   B. A polymeric material in intimate contact with at least one        surface of the electronic device, the polymeric material        comprising (i) an ethylene multi-block copolymer, (ii)        optionally, free radical initiator, e.g., a peroxide or azo        compound, or a photoinitiator, e.g., benzophenone, in an amount        of at least about 0.05 wt % based on the weight of the        copolymer, and (iii) optionally, a co-agent in an amount of at        least about 0.05 wt % based upon the weight of the copolymer.

In another embodiment, the invention is an electronic device modulecomprising:

-   -   A. At least one electronic device, and    -   B. An polymeric material in intimate contact with at least one        surface of the electronic device, the polymeric material        comprising (i) an ethylene multi-block copolymer, and (ii) a        vinyl silane, e.g., vinyl tri-ethoxy silane or vinyl tri-methoxy        silane, in an amount of at least about 0.1 wt % based on the        weight of the copolymer, (iii) a free radical initiator, e.g., a        peroxide or azo compound, or a photoinitiator, e.g.,        benzophenone, in an amount of at least about 0.05 wt % based on        the weight of the copolymer, and (iv) optionally, a co-agent in        an amount of at least about 0.05 wt % based on the weight of the        copolymer.        “In intimate contact” and like terms mean that the polymeric        material is in contact with at least one surface of the device        or other article in a similar manner as a coating is in contact        with a substrate, e.g., little, if any gaps or spaces between        the polymeric material and the face of the device and with the        material exhibiting good to excellent adhesion to the face of        the device. After extrusion or other method of applying the        polymeric material to at least one surface of the electronic        device, the material typically forms and/or cures to a film that        can be either transparent or opaque and either flexible or        rigid. If the electronic device is a solar cell or other device        that requires unobstructed or minimally obstructed access to        sunlight or to allow a user to read information from it, e.g., a        plasma display unit, then that part of the material that covers        the active or “business” surface of the device is highly        transparent.

The module can further comprise one or more other components, such asone or more glass cover sheets, and in these embodiments, the polymericmaterial usually is located between the electronic device and the glasscover sheet in a sandwich configuration. If the polymeric material isapplied as a film to the surface of the glass cover sheet opposite theelectronic device, then the surface of the film that is in contact withthat surface of the glass cover sheet can be smooth or uneven, e.g.,embossed or textured.

Typically, the ethylene multi-block copolymer is an ethylene/α-olefincopolymer with (a) a molecular fraction that elutes between about 40 Cand about 130 C when fractionated using temperature rising effluentfractionation (TREF), characterized in that the fraction has a blockindex of at least 0.5 and up to about 1 and a molecular weightdistribution (PDI, Mw/Mn, MWD) greater than about 1.3, or (b) an averageblock index greater than zero and up to about 1.0 and an MWD greaterthan about 1.3. In addition, the ethylene multi-block copolymertypically has at least one of the following properties: (i) a molecularweight distribution of greater than about 1.3, (ii) a density of lessthan about 0.90 g/cc, (iii) a 2% secant modulus of less than about 150megaPascal (mPa) as measured by ASTM D-882-02, (iv) a melt point of lessthan about 125 C, (v) an α-olefin content of at least about 10 and lessthan about 80 wt % based on the weight of the copolymer, (vi) a Tg ofless than about −35 C, and (vii) a melt index (MI) of less than about100 grams per 10 minutes (g/10 min). The polymeric material can fullyencapsulate the electronic device, or it can be in intimate contact withonly a portion of it, e.g., partially encapsulates the device or islaminated to one face surface of the device. In addition, at least oneadditional film can be interposed between the polymeric material and theelectronic device. Optionally, the polymeric material can furthercomprise a scorch inhibitor, and depending upon the application forwhich the module is intended, the chemical composition of the copolymerand other factors, the copolymer can remain uncrosslinked or becrosslinked. If crosslinked, then it is crosslinked such that itcontains less than about 70 percent xylene soluble extractables asmeasured by ASTM 2765-95.

In another embodiment, the invention is the electronic device module asdescribed in the two embodiments above except that the polymericmaterial in intimate contact with at least one surface of the electronicdevice is a co-extruded material in which at least one outer skin layer(i) does not contain peroxide for crosslinking, and (ii) is the surfacewhich comes into intimate contact with the module. Typically, this outerskin layer exhibits good adhesion to glass. This outer skin of theco-extruded material can comprise any one of a number of differentpolymers, but is typically the same polymer as the polymer of theperoxide-containing layer but without the peroxide. This embodiment ofthe invention allows for the use of higher processing temperatureswhich, in turn, allows for faster production rates without unwanted gelformation in the encapsulating polymer due to extended contact with themetal surfaces of the processing equipment. In another embodiment, theextruded product comprises at least three layers in which the skin layerin contact with the electronic module is without peroxide, and theperoxide-containing layer is a core layer.

In another embodiment, the invention is a method of manufacturing anelectronic device module, the method comprising the steps of:

-   -   A. Providing at least one electronic device, and    -   B. Contacting at least one surface of the electronic device with        a polymeric material comprising (i) an ethylene multi-block        copolymer, (ii) optionally, a free radical initiator, e.g., a        peroxide or azo compound, or a photoinitiator, e.g.,        benzophenone, in an amount of at least about 0.05 wt % based on        the weight of the copolymer, and (iii) optionally, a co-agent in        an amount of at least about 0.05 wt % based upon the weight of        the copolymer.

In another embodiment the invention is a method of manufacturing anelectronic device, the method comprising the steps of:

-   -   A. Providing at least one electronic device, and    -   B. Contacting at least one surface of the electronic device with        a polymeric material comprising (i) an ethylene multi-block        copolymer, (ii) a vinyl silane, e.g., vinyl tri-ethoxy silane or        vinyl tri-methoxy silane, in an amount of at least about 0.1 wt        % based on the weight of the copolymer, (iii) a free radical        initiator, e.g., a peroxide or azo compound, or a        photoinitiator, e.g., benzophenone, in an amount of at least        about 0.05 wt % based on the weight of the copolymer, and (iv)        optionally, a co-agent in an amount of at least about 0.05 wt %        based on the weight of the copolymer.

In a variant on both of these two method embodiments, the module furthercomprises at least one translucent cover layer disposed apart from oneface surface of the device, and the polymeric material is interposed ina sealing relationship between the electronic device and the coverlayer. The cover layer can be rigid, e.g., glass, or flexible, e.g., apolymeric film. “In a sealing relationship” and like terms mean that thepolymeric material adheres well to both the cover layer and theelectronic device, typically to at least one face surface of each, andthat it binds the two together with little, if any, gaps or spacesbetween the two module components (other than any gaps or spaces thatmay exist between the polymeric material and the cover layer as a resultof the polymeric material applied to the cover layer in the form of anembossed or textured film, or the cover layer itself is embossed orotherwise textured).

Moreover, in both of these method embodiments, the polymeric materialcan further comprise a scorch inhibitor, and the method can optionallyinclude a step in which the copolymer is crosslinked, e.g., eithercontacting the electronic device and/or glass cover sheet with thepolymeric material under crosslinking conditions, or exposing the moduleto crosslinking conditions after the module is formed such that thepolyolefin copolymer contains less than about 70 percent xylene solubleextractables as measured by ASTM 2765-95. Crosslinking conditionsinclude heat (e.g., a temperature of at least about 160 C), radiation(e.g., at least about 15 mega-rad if by E-beam, or 0.05 joules/cm² if byUV light), moisture (e.g., a relative humidity of at least about 50%),etc.

In another variant on these method embodiments, the electronic device isencapsulated, i.e., fully engulfed or enclosed, within the polymericmaterial. In another variant on these embodiments, the cover layer istreated with a silane coupling agent, e.g., γ-amino propyl tri-ethoxysilane. In yet another variant on these embodiments, the polymericmaterial further comprises a graft polymer to enhance its adhesiveproperty relative to the one or both of the electronic device and coverlayer. Typically the graft polymer is made in situ simply by graftingthe ethylene multi-block copolymer with an unsaturated organic compoundthat contains a carbonyl group, e.g., maleic anhydride.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of one embodiment of an electronic device moduleof this invention, i.e., a rigid photovoltaic (PV) module.

FIG. 2 is a schematic of another embodiment of an electronic devicemodule of this invention, i.e., a flexible PV module.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term “polymer”, includes both conventional homopolymers, that is,homogeneous polymers prepared from a single monomer, and copolymers(interchangeably referred to as interpolymers), meaning polymersprepared by reaction of at least two monomers or otherwise containingchemically differentiated segments or blocks even if formed from asingle monomer. More specifically, the term “polyethylene” includeshomopolymers of ethylene and copolymers of ethylene and one or more C₃₋₈α-olefins in which ethylene comprises at least 50 mole percent. The term“crystalline” if employed, refers to a polymer that possesses a firstorder transition or crystalline melting point (Tm) as determined bydifferential scanning calorimetry (DSC) or equivalent technique. Theterm may be used interchangeably with the term “semicrystalline”. Theterm “amorphous” refers to a polymer lacking a crystalline melting pointas determined by DSC or equivalent technique.

“Multi-block copolymer”, “segmented copolymer” and like terms refer to apolymer comprising two or more chemically distinct regions or segments(referred to as “blocks”) preferably joined in a linear manner, that is,a polymer comprising chemically differentiated units which are joinedend-to-end with respect to polymerized ethylenic functionality, ratherthan in pendent or grafted fashion. In a preferred embodiment, theblocks differ in the amount or type of incorporated comonomer, density,amount of crystallinity, crystallite size attributable to a polymer ofsuch composition, type or degree of tacticity (isotactic orsyndiotactic), regio-regularity or regio-irregularity, amount ofbranching (including long chain branching or hyper-branching),homogeneity or any other chemical or physical property, Compared toblock copolymers of the prior art, including copolymers produced bysequential monomer addition, fluxional catalysts, or anionicpolymerization techniques, the multi-block copolymers used in thepractice of this invention are characterized by unique distributions ofboth polymer polydispersity (PDI or Mw/Mn or MWD), block lengthdistribution, and/or block number distribution, due, in a preferredembodiment, to the effect of the shuttling agent(s) in combination withmultiple catalysts used in their preparation. More specifically, whenproduced in a continuous process, the polymers desirably possess PDIfrom 1.7 to 3.5, preferably from 1.8 to 3, more preferably from 1.8 to2.5, and most preferably from 1.8 to 2.2. When produced in a batch orsemi-batch process, the polymers desirably possess PDI from 1.0 to 3.5,preferably from 1.3 to 3, more preferably from 1.4 to 2.5, and mostpreferably from 1.4 to 2.

The term “ethylene multi-block copolymer” means a multi-block copolymercomprising ethylene and one or more copolymerizable comonomers, in whichethylene comprises a plurality of the polymerized monomer units of atleast one block or segment in the polymer, preferably at least 90, morepreferably at least 95 and most preferably at least 98, mole percent ofthe block. Based on total polymer weight, the ethylene multi-blockcopolymers used in the practice of the present invention preferably havean ethylene content from 25 to 97, more preferably from 40 to 96, evenmore preferably from 55 to 95 and most preferably from 65 to 85,percent.

Because the respective distinguishable segments or blocks formed fromtwo of more monomers are joined into single polymer chains, the polymercannot be completely fractionated using standard selective extractiontechniques. For example, polymers containing regions that are relativelycrystalline (high density segments) and regions that are relativelyamorphous (lower density segments) cannot be selectively extracted orfractionated using differing solvents. In a preferred embodiment thequantity of extractable polymer using either a dialkyl ether or analkane-solvent is less than 10, preferably less than 7, more preferablyless than 5 and most preferably less than 2, percent of the totalpolymer weight.

In addition, the multi-block copolymers used in the practice of theinvention desirably possess a PDI fitting a Schutz-Flory distributionrather than a Poisson distribution. The use of the polymerizationprocess described in WO 2005/090427 and U.S. Ser. No. 11/376,835 resultsin a product having both a polydisperse block distribution as well as apolydisperse distribution of block sizes. This results in the formationof polymer products having improved and distinguishable physicalproperties. The theoretical benefits of a polydisperse blockdistribution have been previously modeled and discussed in Potemkin,Physical Review E (1998) 57 (6), pp. 6902-6912, and Dobrynin, J. Chem.Phys. (1997) 107 (21), pp 9234-9238.

In a further embodiment, the polymers of the invention, especially thosemade in a continuous, solution polymerization reactor, possess a mostprobable distribution of block lengths. The most preferred polymers usedin the practice of this invention are multi-block copolymers containing4 or more blocks or segments including terminal blocks. In oneembodiment of this invention, the ethylene multi-block copolymers aredefined as having:

(a) a Mw/Mn from about 1.7 to about 3.5, at least one melting point, Tm,in degrees Celsius, and a density, d, in grams/cubic centimeter, wherein the numerical values of Tm and d correspond to the relationship

Tm>−2002.9+4538.5(d)−2422.2(d)², or

(b) a Mw/Mn from about 1.7 to about 3.5, and is characterized by a heatof fusion, ΔH in J/g, and a delta quantity, ΔT, in degrees Celsiusdefined as the temperature difference between the tallest DSC peak andthe tallest CRYSTAF peak, wherein the numerical values of ΔT and ΔH havethe following relationships:

ΔT>−0.1299(ΔH)+62.81 for ΔH greater than zero and up to 130 J/g

ΔT≧48 C for ΔH greater than 130 J/g

wherein the CRYSTAF peak is determined using at least 5 percent of thecumulative polymer, and if less than 5 percent of the polymer has anidentifiable CRYSTAF peak, then the CRYSTAF temperature is 30 C; or

(c) an elastic recovery, Re, in percent at 300 percent strain and 1cycle measured with a compression-molded film of the ethylene/α-olefininterpolymer, and has a density, d, in grams/cubic centimeter, whereinthe numerical values of Re and d satisfy the following relationship whenethylene/α-olefin interpolymer is substantially free of crosslinkedphase:

Re>1481−1629(d); or

(d) has a molecular weight fraction which elutes between 40 C and 130 Cwhen fractionated using TREF, characterized in that the fraction has amolar comonomer content of at least 5 percent higher than that of acomparable random ethylene interpolymer fraction eluting between thesame temperatures, wherein said comparable random ethylene interpolymerhas the same comonomer(s) and has a melt index, density and molarcomonomer content (based on the whole polymer) within 10 percent of thatof the ethylene/α-olefin interpolymer; or

(e) has a storage modulus at 25 C, G′(25 C), and a storage modulus at100 C, G′(100 C), wherein the ratio of G′(25 C) to G′(100 C) is in therange of about 1:1 to about 9:1.

The ethylene/α-olefin interpolymer may also have:

(a) a molecular fraction which elutes between 40 C and 130 C whenfractionated using TREF, characterized in that the fraction has a blockindex of at least 0.5 and up to about 1 and a molecular weightdistribution, Mw/Mn, greater than about 1.3; or

(b) an average block index greater than zero and up to about 1.0 and amolecular weight distribution, Mw/Mn greater than about 1.3.

Suitable monomers for use in preparing the ethylene multi-blockcopolymers used in the practice of this present invention includeethylene and one or more addition polymerizable monomers other thanethylene. Examples of suitable comonomers include straight-chain orbranched α-olefins of 3 to 30, preferably 3 to 20, carbon atoms, such aspropylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene,4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene,1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene; cycloolefinsof 3 to 30, preferably 3 to 20, carbon atoms, such as cyclopentene,cycloheptene, norbornene, 5-methyl-2-norbornene, tetracyclododecene, and2-methyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene; di-and polyolefins, such as butadiene, isoprene, 4-methyl-1,3-pentadiene,1,3-pentadiene, 1,4-pentadiene, 1,5-hexadiene, 1,4-hexadiene,1,3-hexadiene, 1,3-octadiene, 1,4-octadiene, 1,5-octadiene,1,6-octadiene, 1,7-octadiene, ethylidenenorbornene, vinyl norbornene,dicyclopentadiene, 7-methyl-1,6-octadiene,4-ethylidene-8-methyl-1,7-nonadiene, and 5,9-dimethyl-1,4,8-decatriene;aromatic vinyl compounds such as mono- or poly alkylstyrenes (includingstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene and p-ethylstyrene),and functional group-containing derivatives, such as methoxystyrene,ethoxystyrene, vinyl benzoic acid, methyl vinyl benzoate, vinylbenzylacetate, hydroxystyrene, o-chlorostyrene, p-chlorostyrene,divinylbenzene, 3-phenylpropene, 4-phenylpropene, a-methylstyrene, vinylchloride, 1,2-difluoroethylene, 1,2-dichloroethylene,tetrafluoroethylene, and 3,3,3-trifluoro-1-propene.

Other ethylene multi-block copolymers that can be used in the practiceof this invention are elastomeric interpolymers of ethylene, a C₃₋₂₀α-olefin, especially propylene, and, optionally, one or more dienemonomers. Preferred α-olefins for use in this embodiment of the presentinvention are designated by the formula CH₂═CHR*, where R* is a linearor branched alkyl group of from 1 to 12 carbon atoms. Examples ofsuitable α-olefins include, but are not limited to, propylene,isobutylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and1-octene. One particularly preferred α-olefin is propylene. Thepropylene based polymers are generally referred to in the art as EP orEPDM polymers. Suitable dienes for use in preparing such polymers,especially multi-block EPDM type-polymers include conjugated ornon-conjugated, straight or branched chain-, cyclic- or polycyclicdienes containing from 4 to 20 carbon atoms. Preferred dienes include1,4-pentadiene, 1,4-hexadiene, 5-ethylidene-2-norbornene,dicyclopentadiene, cyclohexadiene, and 5-butylidene-2-norbornene. Oneparticularly preferred diene is 5-ethylidene-2-norbornene.

Because the diene containing polymers contain alternating segments orblocks containing greater or lesser quantities of the diene (includingnone) and α-olefin (including none), the total quantity of diene andα-olefin may be reduced without loss of subsequent polymer properties.That is, because the diene and α-olefin monomers are preferentiallyincorporated into one type of block of the polymer rather than uniformlyor randomly throughout the polymer, they are more efficiently utilizedand subsequently the crosslink density of the polymer can be bettercontrolled. Such crosslinkable elastomers and the cured products haveadvantaged properties, including higher tensile strength and betterelastic recovery.

Desirably, the ethylene multi-block copolymers are made with twocatalysts incorporating differing quantities of comonomer, and thesecopolymers have a weight ratio of blocks from 95:5 to 5:95. Theelastomeric polymers desirably have an ethylene content of from 20 to 90percent, optionally a diene content of from 0.1 to 10 percent, and anα-olefin content of from 10 to 80 percent, based on the total weight ofthe polymer. Further preferably, the multi-block elastomeric polymers ofthis embodiment have an ethylene content of from 60 to 90 percent, adiene content of from 0.1 to 10 percent, and an α-olefin content of from10 to 40 percent, based on the total weight of the polymer. Preferredpolymers are high molecular weight polymers, having a weight averagemolecular weight (Mw) from 10,000 to about 2,500,000, preferably from20,000 to 500,000, more preferably from 20,000 to 350,000; apolydispersity less than 3.5, more preferably less than 3.0; and aMooney viscosity (ML (1+4)125 C.) from 1 to 250. More preferably, suchpolymers have an ethylene content from 65 to 75 percent, a diene contentfrom 0 to 6 percent, and an α-olefin content from 20 to 35 percent.

The ethylene multi-block copolymers useful in the practice of thisinvention have a density of less than about 0.90, preferably less thanabout 0.89, more preferably less than about 0.885, even more preferablyless than about 0.88 and even more preferably less than about 0.875,g/cc. The ethylene multi-block copolymers typically have a densitygreater than about 0.85, and more preferably greater than about 0.86,g/cc. Density is measured by the procedure of ASTM D-792. Low densityethylene multi-block copolymers are generally characterized asamorphous, flexible and having good optical properties, e.g., hightransmission of visible and UV-light and low haze.

The ethylene multi-block copolymers useful in the practice of thisinvention have a 2% secant modulus of less than about 150, preferablyless than about 140, more preferably less than about 120 and even morepreferably less than about 100, mPa as measured by the procedure of ASTMD-882-02. The ethylene multi-block copolymers typically have a 2% secantmodulus of greater than zero, but the lower the modulus, the better thecopolymer is adapted for use in this invention. The secant modulus isthe slope of a line from the origin of a stress-strain diagram andintersecting the curve at a point of interest, and it is used todescribe the stiffness of a material in the inelastic region of thediagram. Low modulus ethylene multi-block copolymers are particularlywell adapted for use in this invention because they provide stabilityunder stress, e.g., less prone to crack upon stress or shrinkage.

The ethylene multi-block copolymers useful in the practice of thisinvention typically have a melting point of less than about 125. Themelting point is measured by the differential scanning calorimetry (DSC)method described in WO 2005/090427 (US2006/0199930). Ethylenemulti-block copolymers with a low melting point often exhibit desirableflexibility and thermoplasticity properties useful in the fabrication ofthe modules of this invention.

The ethylene multi-block copolymers used in the practice of thisinvention, and their preparation and use, are more fully described in WO2005/090427, US2006/0199931, US2006/0199930, US2006/0199914,US2006/0199912, US2006/0199911, US2006/0199910, US2006/0199908,US2006/0199907, US2006/0199906, US2006/0199905, US2006/0199897,US2006/0199896, US2006/0199887, US2006/0199884, US2006/0199872,US2006/0199744, US2006/0199030, US2006/0199006 and US2006/0199983.

Due to the unique compositional structure of the ethylene multi-blockcopolymers used in the practice of this invention, these materials oftendo not require crosslinking to achieve the desired properties of aprotective polymer component in an electronic device module,particularly with respect to thermal creep and modulus. In thosecircumstances in which the ethylene multi-block copolymer has aparticularly low density, e.g., less than about 0.86 g/cc, or meltingpoint, e.g., less than about 120 C, then these copolymers are typicallycured or crosslinked at the time of contact or after, usually shortlyafter, the module has been constructed. For low density and/or lowmodulus polymers, crosslinking is important to the performance of theirfunction to protect the electronic device from the environment.Specifically, crosslinking enhances the thermal creep resistance of suchpolymers and the durability of the module in terms of heat, impact andsolvent resistance. If crosslinking is desired, then it can be effectedby any one of a number of different methods, e.g., by the use ofthermally activated initiators, e.g., peroxides and azo compounds;photoinitiators, e.g., benzophenone; radiation techniques other thansunlight and UV light, e.g., E-beam and x-ray; vinyl silane, e.g., vinyltri-ethoxy or vinyl tri-methoxy silane; and moisture cure.

The free radical initiators used in the practice of this inventioninclude any thermally activated compound that is relatively unstable andeasily breaks into at least two radicals. Representative of this classof compounds are the peroxides, particularly the organic peroxides, andthe azo initiators. Of the free radical initiators used as crosslinkingagents, the dialkyl peroxides and diperoxyketal initiators arepreferred. These compounds are described in the Encyclopedia of ChemicalTechnology, 3rd edition, Vol. 17, pp 27-90. (1982).

In the group of dialkyl peroxides, the preferred initiators are: dicumylperoxide, di-t-butyl peroxide, t-butyl cumyl peroxide,2,5-dimethyl-2,5-di(t-butylperoxy)-hexane,2,5-dimethyl-2,5-di(t-amylperoxy)-hexane,2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,2,5-dimethyl-2,5-di(t-amylperoxy)hexyne-3,α,α-di[(t-butylperoxy)-isopropyl]-benzene, di-t-amyl peroxide,1,3,5-tri-[(t-butylperoxy)-isopropyl]benzene,1,3-dimethyl-3-(t-butylperoxy)butanol,1,3-dimethyl-3-(t-amylperoxy)butanol and mixtures of two or more ofthese initiators.

In the group of diperoxyketal initiators, the preferred initiators are:1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-di(t-butylperoxy)cyclohexane n-butyl, 4,4-di(t-amylperoxy)valerate,ethyl 3,3-di(t-butylperoxy)butyrate, 2,2-di(t-amylperoxy)propane,3,6,6,9,9-pentamethyl-3-ethoxycarbonylmethyl-1,2,4,5-tetraoxacyclononane,n-butyl-4,4-bis(t-butylperoxy)-valerate,ethyl-3,3-di(t-amylperoxy)-butyrate and mixtures of two or more of theseinitiators.

Other peroxide initiators, e.g.,00-t-butyl-O-hydrogen-monoperoxysuccinate;00-t-amyl-0-hydrogen-monoperoxysuccinate and/or azo initiators e.g.,2,2′-azobis-(2-acetoxypropane), may also be used to provide acrosslinked polymer matrix. Other suitable azo compounds include thosedescribed in U.S. Pat. Nos. 3,862,107 and 4,129,531. Mixtures of two ormore free radical initiators may also be used together as the initiatorwithin the scope of this invention. In addition, free radicals can formfrom shear energy, heat or radiation.

The amount of peroxide or azo initiator present in the crosslinkablecompositions of this invention can vary widely, but the minimum amountis that sufficient to afford the desired range of crosslinking. Theminimum amount of initiator is typically at least about 0.05, preferablyat least about 0.1 and more preferably at least about 0.25, wt % basedupon the weight of the polymer or polymers to be crosslinked. Themaximum amount of initiator used in these compositions can vary widely,and it is typically determined by such factors as cost, efficiency anddegree of desired crosslinking desired. The maximum amount is typicallyless than about 10, preferably less than about 5 and more preferablyless than about 3, wt % based upon the weight of the polymer or polymersto be crosslinked.

Free radical crosslinking initiation via electromagnetic radiation,e.g., sunlight, ultraviolet (UV) light, infrared (IR) radiation,electron beam, beta-ray, gamma-ray, x-ray and neutron rays, may also beemployed. Radiation is believed to affect crosslinking by generatingpolymer radicals, which may combine and crosslink. The Handbook ofPolymer Foams and Technology, supra, at pp. 198-204, provides additionalteachings. Elemental sulfur may be used as a crosslinking agent fordiene containing polymers such as EPDM and polybutadiene. The amount ofradiation used to cure the copolymer will vary with the chemicalcomposition of the copolymer, the composition and amount of initiator,if any, the nature of the radiation, and the like, but a typical amountof UV light is at least about 0.05, more typically at about 0.1 and evenmore typically at least about 0.5, Joules/cm², and a typical amount ofF-beam radiation is at least about 0.5, more typically at least about 1and even more typically at least about 1.5, megarads.

If sunlight or UV light is used to effect cure or crosslinking, thentypically and preferably one or more photoinitiators are employed. Suchphotoinitiators include organic carbonyl compounds such as such asbenzophenone, benzanthrone, benzoin and alkyl ethers thereof,2,2-diethoxyacetophenone, 2,2-dimethoxy, 2 phenylacetophenone, p-phenoxydichloroacetophenone, 2-hydroxycyclohexylphenone,2-hydroxyisopropylphenone, and 1-phenylpropanedione-2-(ethoxy carboxyl)oxime. These initiators are used in known manners and in knownquantities, e.g., typically at least about 0.05, more typically at leastabout 0.1 and even more typically about 0.5, wt % based on the weight ofthe copolymer.

If moisture, i.e., water, is used to effect cure or crosslinking, thentypically and preferably one or more hydrolysis/condensation catalystsare employed. Such catalysts include Lewis acids such as dibutyltindilaurate, dioctyltin dilaurate, stannous octonoate, and hydrogensulfonates such as sulfonic acid.

Free radical crosslinking coagents, i.e. promoters or co-initiators,include multifunctional vinyl monomers and polymers, triallyl cyanurateand trimethylolpropane trimethacrylate, divinyl benzene, acrylates andmethacrylates of polyols, allyl alcohol derivatives, and low molecularweight polybutadiene. Sulfur crosslinking promoters include benzothiazyldisulfide, 2-mercaptobenzothiazole, copper dimethyldithiocarbamate,dipentamethylene thiuram tetrasulfide, tetrabutylthiuram disulfide,tetramethylthiuram disulfide and tetramethylthiuram monosulfide.

These coagents are used in known amounts and known ways. The minimumamount of coagent is typically at least about 0.05, preferably at leastabout 0.1 and more preferably at least about 0.5, wt % based upon theweight of the polymer or polymers to be crosslinked. The maximum amountof coagent used in these compositions can vary widely, and it istypically determined by such factors as cost, efficiency and degree ofdesired crosslinking desired. The maximum amount is typically less thanabout 10, preferably less than about 5 and more preferably less thanabout 3, wt % based upon the weight of the polymer or polymers to becrosslinked.

One difficulty in using thermally activated free radical initiators topromote crosslinking, i.e., curing, of thermoplastic materials is thatthey may initiate premature crosslinking, i.e., scorch, duringcompounding and/or processing prior to the actual phase in the overallprocess in which curing is desired. With conventional methods ofcompounding, such as milling, Banbury, or extrusion, scorch occurs whenthe time-temperature relationship results in a condition in which thefree radical initiator undergoes thermal decomposition which, in turn,initiates a crosslinking reaction that can create gel particles in themass of the compounded polymer. These gel particles can adversely impactthe homogeneity of the final product. Moreover, excessive scorch can soreduce the plastic properties of the material that it cannot beefficiently processed with the likely possibility that the entire batchwill be lost.

One method of minimizing scorch is the incorporation of scorchinhibitors into the compositions. For example, British patent 1,535,039discloses the use of organic hydroperoxides as scorch inhibitors forperoxide-cured ethylene polymer compositions. U.S. Pat. No. 3,751,378discloses the use of N-nitroso diphenylamine orN,N′-dinitroso-para-phenylamine as scorch retardants incorporated into apolyfunctional acrylate crosslinking monomer for providing long Mooneyscorch times in various elastomer formulations. U.S. Pat. No. 3,202,648discloses the use of nitrites such as isoamyl nitrite, tert-decylnitrite and others as scorch inhibitors for polyethylene. U.S. Pat. No.3,954,907 discloses the use of monomeric vinyl compounds as protectionagainst scorch. U.S. Pat. No. 3,335,124 describes the use of aromaticamines, phenolic compounds, mercaptothiazole compounds,bis(N,N-disubstituted-thiocarbamoyl) sulfides, hydroquinones anddialkyldithiocarbamate compounds. U.S. Pat. No. 4,632,950 discloses theuse of mixtures of two metal salts of disubstituted dithiocarbamic acidin which one metal salt is based on copper.

One commonly used scorch inhibitor for use in free radical, particularlyperoxide, initiator-containing compositions is4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl also known as nitroxyl 2,or NR 1, or 4-oxypiperidol, or tanol, or tempol, or tmpn, or probablymost commonly, 4-hydroxy-TEMPO or even more simply, h-TEMPO. Theaddition of 4-hydroxy-TEMPO minimizes scorch by “quenching” free radicalcrosslinking of the crosslinkable polymer at melt processingtemperatures.

The preferred amount of scorch inhibitor used in the compositions ofthis invention will vary with the amount and nature of the othercomponents of the composition, particularly the free radical initiator,but typically the minimum amount of scorch inhibitor used in a system ofpolyolefin elastomer with 1.7 weight percent (wt %) peroxide is at leastabout 0.01, preferably at least about 0.05, more preferably at leastabout 0.1 and most preferably at least about 0.15, wt % based on theweight of the polymer. The maximum amount of scorch inhibitor can varywidely, and it is more a function of cost and efficiency than anythingelse. The typical maximum amount of scorch inhibitor used in a system ofethylene multi-block copolymer with 1.7 wt % peroxide does not exceedabout 2, preferably does not exceed about 1.5 and more preferably doesnot exceed about 1, wt % based on the weight of the polymer.

Any silane that will effectively graft to and crosslink the ethylenemulti-block copolymer can be used in the practice of this invention.Suitable silanes include unsaturated silanes that comprise anethylenically unsaturated hydrocarbyl group, such as a vinyl, allyl,isopropenyl, butenyl, cyclohexenyl or γ-(meth)acryloxy allyl group, anda hydrolyzable group, such as, for example, a hydrocarbyloxy,hydrocarbonyloxy, or hydrocarbylamino group. Examples of hydrolyzablegroups include methoxy, ethoxy, formyloxy, acetoxy, proprionyloxy, andalkyl or arylamino groups. Preferred silanes are the unsaturated alkoxysilanes which can be grafted onto the polymer. These silanes and theirmethod of preparation are more fully described in U.S. Pat. No.5,266,627. Vinyl trimethoxy silane, vinyl triethoxy silane,γ-(meth)acryloxy propyl trimethoxy silane and mixtures of these silanesare the preferred silane crosslinkers for is use in this invention. Iffiller is present, then preferably the crosslinker includes vinyltriethoxy silane.

The amount of silane crosslinker used in the practice of this inventioncan vary widely depending upon the nature of the ethylene multi-blockcopolymer, the silane, the processing conditions, the graftingefficiency, the ultimate application, and similar factors, but typicallyat least 0.1, preferably at least 1, wt % is used. Considerations ofconvenience and economy are usually the two principal limitations on themaximum amount of silane crosslinker used in the practice of thisinvention, and typically the maximum amount of silane crosslinker doesnot exceed 5, preferably it does not exceed 3, wt % based on the weightof the ethylene multi-block copolymer.

The silane crosslinker is grafted to the ethylene multi-block copolymerby any conventional method, typically in the presence of a free radicalinitiator e.g. peroxides and azo compounds, or by ionizing radiation,etc. Organic initiators are preferred, such as any of those describedabove, e.g., the peroxide and azo initiators. The amount of initiatorcan vary, but it is typically present in the amounts described above forthe crosslinking of the ethylene multi-block copolymer.

While any conventional method can be used to graft the silanecrosslinker to the ethylene multi-block copolymer, one preferred methodis blending the two with the initiator in the first stage of a reactorextruder, such as a Buss kneader. The grafting conditions can vary, butthe melt temperatures are typically between 160 and 260 C, preferablybetween 190 and 230 C, depending upon the residence time and the halflife of the initiator.

In another embodiment of the invention, the polymeric material furthercomprises a graft polymer to enhance the adhesion to one or more glasscover sheets to the extent that these sheets are components of theelectronic device module. While the graft polymer can be any graftpolymer compatible with the ethylene multi-block copolymer of thepolymeric material and which does not significantly compromise theperformance of the copolymer as a component of the module, typically thegraft polymer is a graft polyolefin polymer and more typically, a graftethylene multi-block copolymer that is of the same composition as theethylene multi-block copolymer of the polymeric material. This graftadditive is typically made in situ simply by subjecting the ethylenemulti-block copolymer to grafting reagents and grafting conditions suchthat at least a portion of the ethylene multi-block copolymer is graftedwith the grafting material.

Any unsaturated organic compound containing at least one ethylenicunsaturation (e.g., at least one double bond), at least one carbonylgroup (—C═O), and that will graft to a polymer, particularly apolyolefin polymer and more particularly to an ethylene multi-blockcopolymer, can be used as the grafting material in this embodiment ofthe invention. Representative of compounds that contain at least onecarbonyl group are the carboxylic acids, anhydrides, esters and theirsalts, both metallic and nonmetallic. Preferably, the organic compoundcontains ethylenic unsaturation conjugated with a carbonyl group.Representative compounds include maleic, fumaric, acrylic, methacrylic,itaconic, crotonic, α-methyl crotonic, and cinnamic acid and theiranhydride, ester and salt derivatives, if any. Maleic anhydride is thepreferred unsaturated organic compound containing at least one ethylenicunsaturation and at least one carbonyl group.

The unsaturated organic compound content of the graft polymer is atleast about 0.01 wt %, and preferably at least about 0.05 wt %, based onthe combined weight of the polymer and the organic compound. The maximumamount of unsaturated organic compound content can vary to convenience,but typically it does not exceed about 10 wt %, preferably it does notexceed about 5 wt %, and more preferably it does not exceed about 2 wt%.

The unsaturated organic compound can be grafted to the polymer by anyknown technique, such as those taught in U.S. Pat. Nos. 3,236,917 and5,194,509, For example, in the '917 patent the polymer is introducedinto a two-roll mixer and mixed at a temperature of 60 C. Theunsaturated organic compound is then added along with a free radicalinitiator, such as, for example, benzoyl peroxide, and the componentsare mixed at 30 C until the grafting is completed. In the '509 patent,the procedure is similar except that the reaction temperature is higher,e.g., 210 to 300 C, and a free radical initiator is not used or is usedat a reduced concentration.

An alternative and preferred method of grafting is taught in U.S. Pat.No. 4,950,541 by using a twin-screw devolatilizing extruder as themixing apparatus. The polymer and unsaturated organic compound are mixedand reacted within the extruder at temperatures at which the reactantsare molten and in the presence of a free radical initiator. Preferably,the unsaturated organic compound is injected into a zone maintainedunder pressure within the extruder.

The polymeric materials of this invention can comprise other additivesas well. For example, such other additives include UV-stabilizers andprocessing stabilizers such as trivalent phosphorus compounds. TheUV-stabilizers are useful in lowering the wavelength of electromagneticradiation that can be absorbed by a PV module (e.g., to less than 360nm), and include hindered phenols such as Cyasorb UV2908 and hinderedamines such as Cyasorb UV 3529, Hostavin N30, Univil 4050, Univin 5050,Chimassorb UV 119, Chimassorb 944 LD, Tinuvin 622 LD and the like. Thephosphorus compounds include phosphonites (PEPQ) and phosphites (Weston399, TNPP, P-168 and Doverphos 9228). The amount of UV-stabilizer istypically from about 0.1 to 0.8%, and preferably from about 0.2 to 0.5%.The amount of processing stabilizer is typically from about 0.02 to0.5%, and preferably from about 0.05 to 0.15%.

Still other additives include, but are not limited to, antioxidants(e.g., hindered phenolics (e.g., Irganox® 1010 made by Ciba GeigyCorp.), cling additives, e.g., PIB, anti-blocks, anti-slips, pigmentsand fillers (clear if transparency is important to the application).In-process additives, e.g. calcium stearate, water, etc., may also beused. These and other potential additives are used in the manner andamount as is commonly known in the art.

The polymeric materials of this invention are used to constructelectronic device modules in the same manner and using the same amountsas the encapsulant materials known in the art, e.g., such as thosetaught in U.S. Pat. No. 6,586,271, US Patent Application PublicationUS2001/0045229 A1, WO 99/05206 and WO 99/04971. These materials can beused as “skins” for the electronic device, i.e., applied to one or bothface surfaces of the device, or as an encapsulant in which the device istotally enclosed within the material. Typically, the polymeric materialis applied to the device by one or more lamination techniques in which alayer of film formed from the polymeric material is applied first to oneface surface of the device, and then to the other face surface of thedevice. In an alternative embodiment, the polymeric material can beextruded in molten form onto the device and allowed to congeal on thedevice. The polymeric materials of this invention exhibit good adhesionfor the face surfaces of the device.

In one embodiment, the electronic device module comprises (i) at leastone electronic device, typically a plurality of such devices arrayed ina linear or planar pattern, (ii) at least one glass cover sheet,typically a glass cover sheet over both face surfaces of the device, and(iii) at least one polymeric material. The polymeric material istypically disposed between the glass cover sheet and the device, and thepolymeric material exhibits good adhesion to both the device and thesheet. If the device requires access to specific forms ofelectromagnetic radiation, e.g., sunlight, infrared, ultra-violet, etc.,then the polymeric material exhibits good, typically excellent,transparency for that radiation, e.g., transmission rates in excess of90, preferably in excess of 95 and even more preferably in excess of 97,percent as measured by UV-vis spectroscopy (measuring absorbance in thewavelength range of about 250-1200 nanometers. An alternative measure oftransparency is the internal haze method of ASTM D1003-00. Iftransparency is not a requirement for operation of the electronicdevice, then the polymeric material can contain opaque filler and/orpigment.

In FIG. 1, rigid PV module 10 comprises photovoltaic cell 11 surroundedor encapsulated by transparent protective layer or encapsulant 12comprising an ethylene multi-block copolymer used in the practice ofthis invention. Glass cover sheet 13 covers a front surface of theportion of the transparent protective layer disposed over PV cell 11.Backskin or back sheet 14, e.g., a second glass cover sheet or anothersubstrate of any kind, supports a rear surface of the portion oftransparent protective layer 12 disposed on a rear surface of PV cell11. Backskin layer 14 need not be transparent if the surface of the PVcell to which it is opposed is not reactive to sunlight. In thisembodiment, protective layer 12 encapsulates PV cell 11. The thicknessesof these layers, both in an absolute context and relative to oneanother, are not critical to this invention and as such, can vary widelydepending upon the overall design and purpose of the module. Typicalthicknesses for protective layer 12 are in the range of about 0.125 toabout 2 millimeters (mm), and for the glass cover sheet and backskinlayers in the range of about 0.125 to about 1.25 mm. The thickness ofthe electronic device can also vary widely.

In FIG. 2, flexible PV module 20 comprises thin film photovoltaic 21over-lain by transparent protective layer or encapsulant 22 comprisingan ethylene multi-block copolymer used in the practice of thisinvention. Glazing/top layer 23 covers a front surface of the portion ofthe transparent protective layer disposed over thin film PV 21. Flexiblebackskin or back sheet 24, e.g., a second protective layer or anotherflexible substrate of any kind, supports the bottom surface of thin filmPV 21. Backskin layer 24 need not be transparent if the surface of thethin film cell which it is supporting is not reactive to sunlight. Inthis embodiment, protective layer 21 does not encapsulate thin film PV21. The overall thickness of a typical rigid or flexible PV cell modulewill typically be in the range of about 5 to about 50 mm.

The modules described in FIGS. 1 and 2 can be constructed by any one ofa number of different methods, typically a film or sheet co-extrusionmethod such as blown-film, modified blown-film, calendaring and casting.In one method and referring to FIG. 1, protective layer 12 is formed byfirst extruding an ethylene multi-block copolymer over and onto the topsurface of the PV cell and either simultaneously with or subsequent tothe extrusion of this first extrusion, extruding the same ethylenemulti-block copolymer or a different polymer over and onto the backsurface of the PV cell. Once the protective film is attached the PVcell, the glass cover sheet and backskin layer can be attached in anyconvenient manner, e.g., extrusion, lamination, etc., to the protectivelayer, with or without an adhesive. Either or both external surfaces,i.e., the surfaces opposite the surfaces in contact with the PV cell, ofthe protective layer can be embossed or otherwise treated to enhanceadhesion to the glass and backskin layer. The module of FIG. 2 can beconstructed in a similar manner, except that the backskin layer isattached to the PV cell directly, with or without an adhesive, eitherprior or subsequent to the attachment of the protective layer to the PVcell.

The following prophetic examples further illustrate the invention.Unless otherwise indicated, all parts and percentages are by weight.

Specific Embodiments Example A

A monolayer 15 mil thick protective cast film is made from a blendcomprising 80 wt % ethylene/1-octene multi-block copolymer (5 MI, 0.87g/cc overall density; 30% hard segment, 70% soft segment having adensity of about 0.85 g/cc), 20 wt % maleic anhydride (MAH) modifiedethylene/1-octene (ENGAGE® polyolefin grafted at a level of about 1 wt %MAH and having a post-modified MI of about 1.25 g/10 min and a densityof about 0.87 g/cc), 0.1 wt % of Chimassorb® 944, 0.2 wt % of Naugard®P, and 0.3 wt % of Cyasorb® UV 531. A Solar cell module is preparedusing a solar cell lamination process at 150 C. in which the protectivefilm is located between a transparent superstrate (usually glass) andthe solar cell, and between the solar cell and a backskin material.

Example B

A monolayer 15 mil thick protective cast film is made from a blendcomprising 90 wt % ethylene/1-octene multi-block copolymer (5 MI, 0.87g/cc overall density; 30% hard segment, 70% soft segment having adensity of about 0.85 g/cc), 10 wt % maleic anhydride (MAH) modifiedethylene/1-octene (ENGAGE® polyolefin grafted at a level of about 1 wt %MAH and having a post-modified MI of about 1.25 g/10 min and a densityof about 0.87 g/cc), 0.1 wt % of Chimassorb® 944, 0.2 wt % of Naugard®P, and 0.3 wt % of Cyasorb® UV 531. A Solar cell module is preparedusing a solar cell lamination process at 150 C in which the protectivefilm is located between a transparent superstrate (usually glass) andthe solar cell, and between the solar cell and a backskin material.

Formulation and Processing Procedures:

Step 1: Use ZSK-30 extruder with Adhere Screw to compound resin andadditive package with Amplify.

Step 2: Dry the material from Step 2 for 4 hour at 100 F maximum (useW&C canister dryers).

TABLE 1 Formulation Sample No. 1 Ethylene/1-Octene Multi-Block Copolymer79.3 (5 MI, 0.868 den.) Amplify GR 216 (1.3 MI, 0.879 den - 20 1% MAHgrafted ENGAGE ® Cyasorb UV 531 0.3 Chimassorb 944 LD 0.1 Tinuvin 622 LD0.1 Naugard P 0.2 Total 100

Test Methods and Results:

The adhesion with glass is measured using silane-treated glass. Theprocedure of glass treatment is adapted it from a procedure in Gelest,Inc. “Silanes and Silicones, Catalog 3000 A”.

Approximately 10 mL of acetic acid is added to 200 mL of 95% ethanol inorder to make the solution slightly acidic. Then, 4 mL of3-aminopropyltrimethoxysilane is added with stirring, making a 2%solution of silane. The solution sits for 5 minutes to allow forhydrolysis to begin, and then it is transferred to a glass dish. Eachplate is immersed in the solution for 2 minutes with gentle agitation,removed, rinsed briefly with 95% ethanol to remove excess silane, andallowed to drain. The plates are cured in an oven at 110° C. for 15minutes. Then, they are soaked in a 5% solution of sodium bicarbonatefor 2 minutes in order to convert the acetate salt of the amine to thefree amine. They are rinsed with water, wiped dry with a paper towel,and air dried at room temperature overnight.

The method for testing the adhesion strength between the polymer andglass is the 180 peel test. This is not an ASTM standard test, but it isused to examine the adhesion with glass for PV modules. The test sampleis prepared by placing uncured film on the top of the glass, and thencuring the film under pressure in a compression molding machine. Themolded sample is held under laboratory conditions for two days beforethe test. The adhesion strength is measured with an Instron machine. Theloading rate is 2 in/min, and the test is run under ambient conditions.The test is stopped after a stable peel region is observed (about 2inches). The ratio of peel load over film width is reported as theadhesion strength.

Several important mechanical properties of the cured films are evaluatedusing tensile and dynamic mechanical analysis (DMA) methods. The tensiletest is run under ambient conditions with a load rate of 2 in/min. TheDMA method is conducted from −100 to 120 C.

The optical properties are determined as follows: Percent of lighttransmittance is measured by UV-vis spectroscopy. It measures theabsorbance in the wavelength of 250 nm to 1200 nm. The internal haze ismeasured using ASTM D1003-61.

The results are reported in Table 2. The EVA is a fully formulated filmavailable from Etimex.

TABLE 2 Test Results Key Properties EVA 1 Elongation to break (%) 411.71439.3 STDV 17.5 17.7 Tensile strength at 85° C. (psi) 51.2 71.5 STDV8.9 10 Elongation to break at 85° C. (%) 77.1 107.2 STDV 16.3 16.5Adhesion with glass (N/mm) 7 2 % of transmittance >97 >95 STDV 0.1 0.3Internal Haze 2.8 18.9 STDV 0.4 1.5 STDV = Standard Deviation.

As shown by the data of Table 2, the ethylene/1-octene multi-blockcopolymer provided much superior elongation to break, tensile strengthand elongation to break at 85 C as compared with the EVA polymer withlittle diminution in adhesion to glass strength and optics.

Example C Block Copolymer Polyolefin-Based Encapsulant Film

An ethylene/1-octene block copolymer developed by The Dow ChemicalCompany is used for this example. The density of this resin is 0.877g/cm³ and melt index is 5 g/10 min (measured based on standard ASTMD1238, condition 190 C/2.16 kg). The resin contains 1000 ppm ofantioxidant Irganox-168. Several additives are selected to addfunctionality or improve the long term stability of the resin. Theadditives are UV-absorbent Cyasorb UV 531, UV-stabilizer Chimassorb 944LD, antioxidant Tinuvin 622 LD, vinyltrimethoxysilane (VTMS), andperoxide Luperox-101. The formulation (by weight) is listed in Table 3.

TABLE 3 Film Formulation Formulation Component Weight percentEthylene/1-octene block copolymer 98.45 (MI 5, 0.877 den.) Cyasorb UV531 0.3 Chimassorb 944 LD 0.1 Tinuvin 622 LD 0.1 Irganox-168 Silane (DowCorning Z-6300) 1 Luperox-101 0.05 Total 100

TABLE 4 Ethylene/1-Octene Block Copolymer Composition Overall OcteneOctene Overall Octene Octene Octene in soft in hard Octene in soft inhard (mol %) (mol %) (mol %) (wt %) (wt %) (wt %) 12.7 17.8 0.8 36.846.4 3.1

TABLE 5 Ethylene/1-Octene Block Copolymer Physical Properties Heat ofDensity I₁₀/ Mw Mn Mw/ Fusion T_(m) T_(c) Property (g/cm³) I₂ I₁₀ I₂(g/mol) (g/mol) Mn (J/g) (° C.) (° C.) 0.877 5.0 35.7 7.1 85090 331302.6 50 123 102

Sample Preparation

Ethyene/1-octene block copolymer pellets are dried at 40° C. overnightin a dryer. The pellets and the additives are dry mixed and placed in adrum and tumbled for 30 minutes. Then the silane and peroxide are pouredinto the drum and tumbled for another 15 minutes. The well mixedmaterials are fed to a film extruder for film casting. Film is cast on afilm line (Killion Single Screw Extruder, 24 inches sheet die), and theprocessing conditions are summarized in Table 6

TABLE 6 Process Conditions Ext. Form. Head Zone 1 Zone 2 Zone 3 Ad. DieAd. Die # RPM Amp P (psi) (F) (F) (F) (F) (C) (C) 2 30 20 2,600 300 350360 375 192 180

An 18-19 mil thick film is saved at 5.9 ft./min. The film sample issealed in an aluminum bag to avoid UV irradiation and moisture.

Test Methods and Results

The following key properties of the film are tested.

1. Optical Property:

The light transmittance of the film is examined by UV-visiblespectrometer (Perkin Elmer UV-Vis 950 with scanning double monochromatorand integrating sphere accessory) after compression molding the initialcast film at a temperature of about 150 C for 30 minutes andsubsequently quenching to room temperature by placing the film between 2cold (20 C) platens, to achieve a final film thickness of about 15 mils.Samples used in this analysis are 15 mil thick. The UV-Visible spectraof the film is compared to a commercial incumbent film for the sameapplication. Both films show above 90% of transmittance over thewavelength range from 400 nm to 1100 nm.

2. Adhesion to Glass:

The method used to measure adhesion test is a 180° peel test. This isnot an ASTM standard test, but has been used to examine the adhesionwith glass for PV module and auto laminate glass applications. The testsample is prepared by placing the film on the top of glass underpressure in a compression molding machine. The desired adhesion width is1 in. A Teflon sheet is placed between the glass and the material toseparate the glass and polymer for the purpose of test setup. Theconditions for the glass/film sample preparation are listed below:

1) 160° C. for 3 min at 2000 lbs

2) 160° C. for 30 min at 8000 lbs

3) Cool to room temperature at 8000 lbs.

4) Remove the sample from the chase and allow 48 hours for the materialto condition at room temperature before the adhesion test.

The adhesion strength is measured with a materials testing system(Instron 5581). The loading rate is 2-inches per minute and the testsare run at ambient conditions (24° C. and 50% RH). A stable peel regionis needed (about 2 inches) to evaluate the adhesion to glass. The ratioof peel load in the stable peel region over the film width was reportedas the adhesion strength.

The effect of temperature and moisture on adhesion strength is examinedusing samples aged in hot water (80° C.) for one week. These samples aremolded on glass, then immersed in hot water for one week. These samplesare then dried under lab conditions for two day before the adhesiontest. In comparison, the adhesion strength of a commercial film is alsoevaluated under the same conditions. The adhesion strength of film and acommercial sample are shown in Table 7.

TABLE 7 Results of Adhesion Test to Glass Conditions for Adhesion SampleMolding on Aging Strength Information Glass Condition (N/mm) Commercialfilm 160 C., one hr none 10 (cured) Commercial (cured) 160 C., one hr 80C. in water 1 for one week Inventive film 160 C., 0.5 hr none >10 (nodelamination) Inventive film 160 C., 0.5 hr 80 C. in water 10 for oneweek

3. Water Vapor Transmission Rate:

The water vapor transmission rate (WVTR) is measured using a permeationanalysis instrument (Mocon Permatran W Model 101 K). All WVTR units arein grams per 100-square inches per day (g/(100 in²-day) measured at 38 Cand 50 C and 100% relative humidity (RH), average of two specimens.Commercial film is also tested to compare the moisture barrierproperties. The experimental film and the commercial film thickness are15 mil, and both films are cured at 160° C. for 30 minutes. The resultsof WVTR are shown in Table 8.

TABLE 8 WVTR Test Results WVTR at WVTR at 38 C. 50 C. Thick Permeationat 38 C. Permeation at 50 C. Film Specimen g/(m²-day) g/(m²-day) mil)(g-mil)/(m²-day) (g-mil)/(m²-day) Commercial A 44.52 98.74 16.80 7371660 Film B 44.54 99.14 16.60 749 1641 avg. 44.53 98.94 16.70 743 1650Inventive A 5.31 12.78 18.60 99 238 Film B 13.13 18.80 246 avg. 5.3112.95 18.70 99 242

As the data in Table 8 shows, the WVTR of the inventive film is muchless permeable to water vapor than the commercial film.

Although the invention has been described in considerable detail throughthe preceding description and examples, this detail is for the purposeof illustration and is not to be construed as a limitation on the scopeof the invention as it is described in the appended claims. All UnitedStates patents, published patent applications and allowed patentapplications identified above are incorporated herein by reference.

1. An electronic device module comprising: A. At least one electronicdevice, and B. An polymeric material in intimate contact with at leastone surface of the electronic device, the polymeric material comprising(1) an ethylene multi-block copolymer with at least one property of (a)a molecular weight distribution of greater than about 1.3, (b) a densityof less than about 0.90 g/cc, (c) a 2% secant modulus of less than about150 megaPascal (mPa) as measured by ASTM D-882-02, (d) a melt point ofless than about 125 C, (e) an α-olefin content of at least about 10 andless than about 80 weight percent (wt %) based on the weight of thecopolymer, and (f) a Tg of less than about −35 C, (2) optionally, a freeradical initiator, and (3) optionally, a co-agent.
 2. The module ofclaim 1 in which the electronic device is a solar cell.
 3. The module ofclaim 2 in which the free radical initiator is present in an amount ofat least about 0.05 wt % based on the weight of the copolymer.
 4. Themodule of claim 3 in which the coagent is present in an amount of atleast about 0.05 wt % based on the weight of the copolymer.
 5. Themodule of claim 4 in which the free radical initiator is a peroxide. 6.The module of claim 1 in which the polyolefin copolymer is crosslinkedsuch that that the copolymer contains less than about 70 percent xylenesoluble extractables as measured by ASTM 2765-95.
 7. The module of claim1 in which the polymeric material is in the form of a monolayer film inintimate contact with at least one face surface of the electronicdevice.
 8. The module of claim 1 in which the polymeric material furthercomprises a scorch inhibitor in an amount from about 0.01 to about 1.7wt %.
 9. The module of claim 1 further comprising at least one glasscover sheet.
 10. The module of claim 1 in which the polymeric materialfurther comprises a polyolefin polymer grafted with an unsaturatedorganic compound containing at least one ethylenic unsaturation and atleast one carbonyl group.
 11. The module of claim 10 in which theunsaturated organic compound is maleic anhydride.
 12. The module ofclaim 1 in which the ethylene multi-block copolymer is furthercharacterized by at least one of (i) a molecular fraction that elutesbetween about 40 C and about 130 C when fractionated using TREF,characterized in that the fraction has a block index of at least 0.5 andup to about 1 and a MWD greater than about 1.3, and (ii) an averageblock index greater than zero and up to about 1.0 and an MWD greaterthan about 1.3.
 13. An electronic device module comprising: A. At leastone electronic device, and B. A polymeric material in intimate contactwith at least one surface of the electronic device, the polymericmaterial comprising (1) an ethylene multi-block copolymer with at leastone property of (a) a molecular weight distribution of greater thanabout 1.3, (b) a density of less than about 0.90 g/cc, (c) a 2% secantmodulus of less than about 150 megaPascal (mPa) as measured by ASTMD-882-02, (d) a melt point of less than about 125 C, (e) an α-olefincontent of at least about 10 and less than about 80 wt % based on theweight of the copolymer, and (f) a Tg of less than about −35 C, (2) avinyl silane in an amount of at least about 0.1 wt % based on the weightof the copolymer, (3) free radical initiator in an amount of at leastabout 0.05 wt % based on the weight of the copolymer, and (4)optionally, a co-agent.
 14. The module of claim 13 in which theelectronic device is a solar cell.
 15. The module of claim 14 in whichthe coagent is present in an amount of at least about 0.05 wt % based onthe weight of the copolymer.
 16. The module of claim 15 in which thefree radical initiator is a peroxide.
 17. The module of claim 16 inwhich the vinyl silane is at least one of vinyl tri-ethoxy silane andvinyl tri-methoxy silane.
 18. The module of claim 13 in which thepolyolefin copolymer is crosslinked such that that the copolymercontains less than about 70 percent xylene soluble extractables asmeasured by ASTM 2765-95.
 19. The module of claim 13 in which thepolymeric material is in the form of a monolayer film in intimatecontact with at least one face surface of the electronic device.
 20. Themodule of claim 13 in which the polymeric material further comprises ascorch inhibitor in an amount from about 0.01 to about 1.7 wt %.
 21. Themodule of claim 13 in which the polymeric material further comprises apolyolefin polymer grafted with an unsaturated organic compoundcontaining at least one ethylenic unsaturation and at least one carbonylgroup.
 22. The module of claim 21 in which the unsaturated organiccompound is maleic anhydride.
 23. The module of claim 13 in which theethylene multi-block copolymer is further characterized by at least oneof (i) a molecular fraction that elutes between about 40 C and about 130C when fractionated using TREF, characterized in that the fraction has ablock index of at least 0.5 and up to about 1 and a MWD greater thanabout 1.3, and (ii) an average block index greater than zero and up toabout 1.0 and an MWD greater than about 1.3.
 24. An electronic devicemodule comprising: A. At least one electronic device, and B. A polymericmaterial in intimate contact with at least one surface of the electronicdevice, the polymeric material comprising an ethylene multi-blockcopolymer.
 25. An ethylene/non-polar alpha-olefin polymeric filmcharacterized in that the film has (i) greater than or equal to 92%transmittance over the wavelength range of 400 to 1100 nanometers, and(ii) a water vapor transmission rate of less than about 50 grams persquare meters per day (g/m²-day).